339th

339th may refer to:


 * 339th Aviation Detachment, United States Army Aviation Branch
 * 339th Bombardment Group, unit of the New York Air National Guard
 * 339th Bombardment Squadron, inactive United States Air Force unit
 * 339th Fighter Group, unit of the United States Air Forces during World War II
 * 339th Flight Test Squadron, United States Air Force unit
 * 339th Infantry Regiment (United States), infantry regiment of the United States Army
 * 339th Rifle Division (Soviet Union), formed in 1941 as a standard Red Army rifle division at Rostov-on-Don
 * 339th Transportation Company (Direct Support), United States Army and Transportation Corps
 * 339th Troop Carrier Squadron, component of the 419th Operations Group